This plastic film containing hydrophobic and ion-exchange resins captures molecules on the surface of art.

Credit: Anal. Chem.

This plastic film containing hydrophobic and ion-exchange resins captures molecules on the surface of art.

Credit: Anal. Chem.

Beyond their beauty and cultural significance, art objects are covered with chemicals that provide a window into their history—how they were created, taken care of, and where they’ve been. But conservators have limited options for analyzing the surface chemicals without damaging the irreplaceable artwork. In a bid to help, a research team has reported an updated version of a noninvasive method for removing molecules from a range of surfaces and analyzing them using mass spectrometry (Anal. Chem. 2017, DOI: 10.1021/acs.analchem.6b03722). Pier Giorgio Righetti of Politecnico di Milano and his colleagues previously developed an extruded plastic film made from ground-up hydrophobic and cation-exchange resin beads contained in a poly(ethylene-vinyl acetate) binder. They’ve now added anion-exchange beads to expand the range of compounds that can be detected. They dampen a strip of the film with water and set it on a surface of interest to draw chemicals into the film for analysis. The researchers next elute proteins with an ammonium acetate buffer, and they recover dye molecules with a mixture of methanol and formic acid. Then they analyze the compounds using LC/MS. The team tested the method on parchment, canvas, bone, and linens. In addition, they analyzed two 16th-century frescoes and a 14th-century wood painting and found proteins and dyes consistent with the times. Tests of reference molecules on control materials showed that the process removes no more than 10% of the compounds, meaning the technique is noninvasive, the researchers say.